Rocky Mountain Spotted Fever

Rocky Mountain Spotted Fever, a tick-borne disease


Rocky Mountain spotted fever is transmitted to people by the bite of a tick infected with the bacterial organism Rickettsia rickettsii, or by contamination from the contents of an attached tick when it is removed (from a person or animal). Tweezers should be used to remove ticks, along with a paper towel or rubber gloves to shield contact.
The primary carriers of Rocky Mountain spotted fever in the United States are the American dog tick, Dermacentor variabilis, and the Rocky Mountain wood tick, Dermacentor andersoni.
Insect Shield tick repellent hiking socks are an excellent way to prevent bites that can cause Rocky Mountain spotted fever and many other tick-borne diseases.
First recognized in 1896 in Idaho, Rocky Mountain spotted fever has a misleading name because the United States’ highest incidence of the disease occurs in North Carolina and Oklahoma. In fact, relatively few cases are reported in the Rocky Mountain states. Each year from April through September, approximately 800 to 1,200 cases are reported in the United States, more than half of which occur in the Southeast (Maryland to Florida).

Rocky Mountain spotted fever is a serious disease, and it is likely that many cases are not reported. Initial symptoms, which can resemble other illnesses, usually appear about 5-10 days after a tick bite and can include fever, nausea, vomiting, severe headache, muscle pain and lack of appetite. Further symptoms include a rash, abdominal pain, joint pain and diarrhea. The rash generally appears 2-5 days after the onset of fever. Children and young people typically develop a rash earlier than older persons, but about 10-15% of patients never develop a rash.

Rocky Mountain spotted fever usually requires hospitalization. Cells lining blood vessels are infected, and the respiratory, gastrointestinal, renal and central nervous systems can be affected. The occurrence of severe or fatal Rocky Mountain spotted fever has been linked to advanced age, male sex, African-American race, chronic alcohol abuse and deficiency of a specific enzyme (G6PD). People who survive acute infection can develop chronic health problems including partial paralysis of the lower extremities, gangrene, hearing loss, loss of bowel or bladder control and language disorders.

There is no vaccine for Rocky Mountain spotted fever, but there are laboratory tests to confirm the disease, and early treatment with antibiotics proves effective. In fact, prompt and appropriate treatment is imperative. According to the Centers for Disease Control and Prevention (CDC), approximately 3-5 % of cases are fatal.
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Detailed Information:

What is Rocky Mountain spotted fever and how is it transmitted?

Rocky Mountain spotted fever is caused by a small bacterium, Rickettsia rickettsii, which is transmitted by members of the hard tick family, Ixodiae. The two major tick vectors in the United States include the dog tick, Dermacentor variabilis, and the Rocky Mountain wood tick, Dermacentor andersoni.
Dermacentor variabilis tick species
United States Distribution of Dermacentor variabilis, or dog tick

Dermacentor variabilis                distribution of dog tick

Dermacentor andersoni, rocky mountain wood tick
United States Rocky Mountain Wood Tick Distribution

Dermacentor andersoni              distribution of Rocky Mountain wood tick

The dog tick prefers dogs as hosts, but it feeds readily on other large mammals including people. Larvae and nymphs of the Rocky Mountain wood tick feed on rodents and other small animals, and adults feed on large mammals.

Rickettsia is transmitted through the saliva of an infected tick. It usually takes several hours of feeding for transmission to occur, and the proportion of infected ticks is low—approximately 1%-3% of the population in areas where human cases have been reported.

In people, rickettsia infects the cells that line small to medium blood vessels, causing the cells to become damaged and die. This results in the leakage of plasma and blood into tissues adjacent to the cells—which creates the typical Rocky Mountain spotted fever rash, and can damage tissues and organs. Severe cases may involve the respiratory, gastrointestinal, nervous and renal systems. Long-term complications of Rocky Mountain spotted fever, particularly in those with severe disease, include paralysis of the lower extremities, gangrene requiring amputation of limbs, toes or fingers, loss of bowel and bladder control, as well as movement and language disorders.
Early clinical signs of Rocky Mountain spotted fever resemble those of other viral diseases, and include nausea, headache, muscle pain and lack of appetite. About 2-5 days after onset of fever, a rash appears consisting of small, flat, pink, non-itchy spots on the wrists and forearms. Later symptoms include rash, joint pain, abdominal pain and diarrhea. The characteristic red, Rocky Mountain spotted fever rash is usually not seen until after the sixth day of fever onset, and occurs on the palms and soles of the feet.
Photo depicted Rocky Mountain Wood Tick Rash

Rocky Mountain spotted fever rash

How many cases of Rocky Mountain spotted fever occur annually in the United States?

Between 250 and 1,200 cases of Rocky Mountain spotted fever occur each year.

How is Rocky Mountain spotted fever treated?

Because it is a bacterial infection, Rocky Mountain spotted fever is treatable with antibiotics, usually doxycycline. Patients generally respond well to treatment if started early, and the fever usually subsides within 72 hours. If Rocky Mountain spotted fever is not treated promptly, possible organ damage and failure means patients will need more intensive care. Infection generally confers lifelong immunity.

How can I protect myself from Rocky Mountain spotted fever?

You should take measures to prevent tick bites. Insect Shield® Repellent Apparel is proven and registered to repel ticks—as well as mosquitoes, ants, flies and chiggers. The United States Environmental Protection Agency (EPA) requires extensive effectiveness data to prove a product's ability to repel insects. Many species and varieties of these insects have been tested, including those that carry dangerous diseases such as Rocky Mountain spotted fever.